Safe Mode is very difficult to access with Windows 8. However, you could boot with a Windows install disk and do a repair / non-destructive install. To do this, you will need to connect (and boot from) an external USB CD/DVD drive. You will also need to get a Windows install disk that is the exact same version of Windows that is currently on your computer.

Power off your computer; get an external USB CD/DVD drive, and connect it to your computer. Put the Windows disk in the drive.

Now power on your computer. Hit ESC several times as soon as it powers on; this will bring you to a start menu, where you can then hit F10 to go into the computer setup.

In the setup, go to the Boot Order, and select USB CD/DVD (or something similar to that) as your first boot device.

Save the settings, then reboot. It will boot from the external DVD drive.